The invention relates to a method and to a device for opening and closing a valve of an internal combustion engine.
Known are the camshaft-controlled valve actuation, the electromagnetic control and the hydraulic valve control. The invention is principally based on the electromagnetic valve control (EMVC). However, it can be applied in connection with other valve controls as well, for example such as the hydraulic or the pneumatic valve control.
The EMVC has been structured until now in the form of an oscillator comprising one mass, whereby an armature is oscillating back and forth between two magnetic coils. The armature is connected with the valve. In the currentless condition, the armature is located in about the center between the two magnetic coils. Because of the large gap in the idle position and the poor efficiency connected therewith, a relatively high expenditure of energy is required during acceleration, which per se makes the feasibility of the electromagnetic valve control questionable in series applications, to begin with.
For reducing the energy requirement and in particular for the purpose of minimizing the so-called armature thumping and thus the noise, DE 197 23 405 A1 discloses a method by which a defined rate of impact of the armature can be adjusted when the valve is closing.
A drawback has to be seen in the fact that valve niches have to be worked into the piston in order to safely prevent the valve from coming into contact with the piston, or that the wall of the combustion chamber has to be recessed in the cylinder head. In terms of combustion technology, such measures represent a negative influence on the combustion chamber.
Therefore, the invention is dealing with the problem of reducing the use of energy in connection with electromagnetic or hydraulic valve controls and to avoid any negative influence on the combustion process exerted on the cylinder head by valve niches or recessed walls of the combustion chamber.
Said problem is solved in connection with methods of the type specified above by the characterizing features specified in claim 1. In conjunction with devices of the type specified above, the problem is solved by the characterizing features specified in claim 4 or 5. Advantageous further developments of the invention are the objects of the dependent claims.
The basic idea of the invention is to transmit the kinetic energy, and possibly of a mass component connected with the valve, such energy being contained in the valve at the end of the closing process, to a body of mass, and to store such energy there intermediately, so that this energy is available for the next opening stroke of the valve. In such a process, the pulse or mechanical pulse can be transmitted in each case directly between the bodies of mass, or passed on via at least one intermediate member, whereby the intermediate member is either arranged stationary to the greatest possible extent, or connected with one of the two masses. If the body of mass is to be retained, for example, by a magnet, the energy is intermediately stored in a spring, as a rule that exerts a resetting force on the body of mass.
Physically speaking, the known EMVC represents a pendulum comprising one mass, whereas the invention can be described as a pendulum comprising two masses with energy transmission.
The known one-mass oscillation of the EMVC is divided in this connection in two semi-oscillations with two masses. At the end of each semi-oscillation, the kinetic energy is transferred to the second oscillating mass by a shock pulse. Through suitable coordination, for example via the spring rate, the basic duration of the oscillation of the valve is adjusted at the ratio of xe2x80x9cthree cycles closedxe2x80x9d to xe2x80x9cone cycle openedxe2x80x9d.
Therefore, a variation of the oscillation times can be realized by adjusting the initial tension of the spring and/or the stiffness of the spring, on the one hand, and with the help of known means such as magnetic retention in the end positions on the other.
The following advantages are obtained as compared to the known EMVC:
The valve remains closed without external energy feed because the energetic zero-position is present in the closed condition. If necessary, the valve can be pressed also into the valve seat by spring force.
Undefined operating points are avoided because a clear idle position is available in the cycle of the valve movement.
The swing-in takes place in a controlled manner; contact of the valve with the piston can be excluded. This means that the combustion chamber can be designed in an optimal manner, especially without valve niches.
Due to the pulse-like transmission it is possible to realize very steep opening flanks, or very rapid opening of the valve is made possible.
The valve opening duration can be varied without changing the initial tension of the spring.